Fire control selector for automatic firearms



June 27, 1950 A.F. GAIDOS FIRE CONTROL SELECTOR FOR AUTOMATIC FIREARMS Original Filed July 3, 1946 Patented June 27, 1950 UNITED STATES TENT OFFICE Alonzo F. Gaidos, Redwood, Calif.

Original application July 3, 1946, Serial No.

Divided and this application March 25, 1948, Serial No. 16,897

4 Claims. (01. 89-140) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for govermnental purposes, without the payment to me of any royalty thereon.

This invention relates to an improved fire control mechanism for firearms of the semi-automatic type.

This application is a division of my application for Fire Control Mechanism, Serial No. 681,281 filed July 3, 1946.

It is an object of this invention to provide a simple fire control mechanism to convert a semiautomatic firearm to selectively obtain full automatic fire without the necessity of performing major machining operations on existing components.

A particular object of this invention is to provide a fire control mechanism for a firearm commonly known as the U. S. carbine, cal. .30, M1 which as issued, affords only means to fire the weapon semi-automatically.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a partial side elevational view of a firearm shown with the stock removed which embodies the preferred form of this invention. In such figure the inertia member isshown in the retracted position and the hammer latch is engaged by the hammer.

Fig. 1A is a continuation of Fig. 1.

Fig. 2 is a fragmentary detail view showing the forward end of the actuating bar engaging the front end of the inertia member of the firearm.

Fig. 3 is a fragmentary detail top elevational view of the trigger guard shown with the hammer removed to illustrate the selector mechanism.

Fig. 4 is a fragmentary detail cross-sectional view taken along the line I4 of Fig. 1.

Fig. 5 is a fragmentary detail view shown partly in longitudinal section to illustrate the conventional sear mechanism of the firearm.

Fig. 6 is a detail fragmentary view of Fig. 1 showing the hammer latch released from engagement with the hammer by the actuating bar.

Fig. 7 is a perspective view of the hammer latch.

Fig. 8 is a cross-sectional view taken along the line 88 of Fig. 3.

Fig. 9 is a perspective view of the selector.

While not limited thereto, the invention is particularly applied to semi-automatic firearms of the type having a reciprocating operating slide which functions the bolt between its locked, battery position and an unlocked, recoiled position.

In Fig. 1 there is shown in assembled relation a firearm of the semi-automatic type embodying this invention. The major elements of such firearms are substantially identical to the U. S. carbine, cal. .30 Ml which, as is commonly known, is constructed to fire semi-automatically. Such firearm comprises mainly a receiver I, a barrel 2, a bolt 3 and a trigger guard 4. Barrel 2 is threadably secured to receiver I in a conventional manner and trig er guard 4 is mounted on the underside of receiver I. oppositely disposed ribs 5 (Fig. 4) provided on the rear end of receiver I engage corresponding ways 6 in trigger guard 4. The forward end of such trigger guard is secured to the receiver by a transverse headed pin I.

Bolt 3 is horizontally mounted within receiver I and reciprocates therein on suitable horizontal.

ways provided on the interior of such receiver. On the underside of barrel 2 there is slidably' mounted an operating slide II and such slide is connected to bolt 3 by the rearwardly projecting offset handle portion I la of such slide. The ele-. ments thus far described are all conventional.

In the preferred modification of this invention, an actuating bar I4 is provided which is slidably mounted on the left side of receiver l as shown in Figs. 1 and 2. The forward end of bar I4 terminates in a hook I5 which is bent inwardly and engages the forward end of operating slide II. The rear end It of bar I4 is of substantially greater width. Aforwardly opening slot I1 is provided on the front end of enlarged portion I6 which is engaged by headed pin 1. The wood of the stock (not shown) prevents removal of the pin. A cam slot I8 is cut in portion Hi. The forward end 20 of cam slot I8 is enlarged to permit assembly of actuating bar I4 to a hammer latch I9.

A conventional trigger 2| and sear 22 (Figs. 1, 3, 5 and 8) are pivotally mounted in trigger guard 4 on a novel selector 23. A sear spring 31 is mounted between sear 22 and trigger 2| urging sear 22 forwardly. Selector 23 comprises a shaft portion 24 and a knob portion 25, such knob portion being preferably formed integrally with shaft 24 and is located exteriorly of the trigger guard to permit convenient manual rotation thereof. Shaft 24 is of enlarged diameter immediately adjacent a hub I2 provided on the inside face of knob 25 as shown at 26. A central portion 21 of shaft 24 is eccentrically formed with respect to the axis of shaft 24. The eccentric portion 21 passes through a slot-like hole .28 in sear 22. Two oppositely disposed 2,512,688 31;; .r v i v j 2| is pulled rearwardly and held there by pressure of the finger, the front end of sear 22 will disengage from sear notch 38. However sear 22 is pr vented from moving forward to a cookin position relative to hammer 34 by eccentric 21 and hence sear 22 does not re-engage hammer -34 2 until trigger 2I, is again released. Thus it is apparent that changing the longitudinal position of sear 22' by rotation: of selector 23 to limit the movement of such sear relative to hammer 34,

I will, provide semi-automatic or full automatic in transversely projecting relation to the for- Y ward end thereof. Such stud engages the cam slot I8 of actuating bar I4 and actuating bar I4 fire respectively. It is desired to point out that full automatic fire can be stopped at will by simply releasing the trigger which brings the front is assembled to the gun by inserting the headed engage pin 1 in slot I! and hook end .I 'with" slide H. An inwardly projecting lug or ear 33 is. provided approximately in the centerof latch Hand is shaped to engage the hammer 34 of the firearm and prevent hammer 34, from rotating forwardly to fire the gun except when. the bolt is in battery position, as' will be presently described. Detent 3| is formed by bending one end of a torsion spring 35. Such spring is mounted on a pin 36 which is also utilized to pivotally moimt hammer 34'. The other end of torsion spring 35. is hooked about trigger guard 4 as, shown in Fig. 3. I I

.For semi-automatic fire, selector 23 is turned as shown in Fig. 1. In such position detent 3I engages one of the notches 29. thereby yieldingly securingselector 2.3 in the selected position. .Ec centric portion 2'! on such selector 23 .is, then in a forward position and as such eccentric lies within slot-like hole 28 of sear 22, the sear is biased forwardly by sear spring 3?. When hammar 34, is. rotated rearwardly about pin .33 "by recoil movement of the bolt 3, the forward end of sear v22 engages asear notch 38 provided on the lower rear end of hammer ,34. Sear 22 is forced rearwardly by thegreater'bias of hammer spring III]vv and the rear end thereof then comes to rest on top. of an, upstanding projection, 39 provided on trigger .2 I

When such trigger is pulled rearwardly, the forwardend of scar 22 isdisengaged from sear notch 38 releasing hammer v34. As the load of hammer spring 40 is removed from sear 2.2, the bias. of sear spring 31 urges sear 2,2 forwardly so that the rear end of scar 22 drops .off projection 39-. Can the recoil stroke of bolt.3,v the for ward end. of sear ,22 again engages sear notch 38. of hammer34 thereby holding. such hammer in the. cocked position irrespective of the fact that the trigger remains pulled. Hammer 34 can not be released until the pressure of the finger is removed from trigger. 2|, because sear;22 is inthe so-called disconnected position. That is, the rear end of sear 22 lies forward of andv abutting trigger projection 39 and sear 22 Loan not be disengaged from hammer '34 until trigger 2I is permitted to-move forwardly sufliciently to permit the bias of hammer 34 to force-the rear end of sear 22 rearwardly onto projection 39. Then sear 22 can be released and the gun fired by another, pull on trigger 2 I. 1

. To effect automatic fire, selector 23 is rotated 180 in which position detent 3| then engages the other notch 29 on the-selector. -Such:rota-- tion'moves eccentric portion 2'! of'selector shaft 24 rearwardly, hence limiting the forward movement :ofsea-r ,22. In this position, when trigger end of scar 22' into the path of notch 38 of the hammer and permits hammer 34 to force the rear end of sear 22 onto projection 39 thereby holding: hammer:,34, in the cooked position ready for release'by the next pull of the trigger.

In full automatic fire, it is apparent to one skilled in the art that sear 22 is disengaged entirely-fromhammer 3,4, and if no other means: wereprovid ed, the hammer would follow the bolt. firing the gun when theiorward movement of the bolt was arrested, independent, or" whether thegbolt is fully rotated into its locked position, Hence it is highly desirable to momentarily delay the fall of hammer v34 until bolt 3 is fully locked,- otherwise there would be danger ofpremature discharge of the cartridgewith harr n ful results, or at any event, a lighter blow would besupported, by the hammer since it, would fol-. low the bolt forward.

Hammer latch I9 therefore is arranged to hold hammer 34 in the cooked position until bolt 3 is fully locked before such hammer is released. action isv effective in both automatic and semiautomatic fire, When operating slide II drives rearwardly upon discharge of a cartridge from force imparted by a piston (not shown), ham,- mer 34 is rotated to its cocked position by bolt 3. If trigger 2| is. not held rearwardly, sear 22 will engage sear notch 38. thereby holding hammer 34 in the cooked position until release of such is eifectedby pulling trigger2l. On the. other hand if trigger 2| is held rearwardly when bolt (3.119.- coils, hammer 34'will not be blocked by sear .22.

However, as slide H is. forced rearwardly, the rear endof suchslide strikes an integral lug AI providedon the inside of bar 14 just slightly ahead of receiver I as shown in Fig. 17A. Hence. slide II forces bar I4 rearwardly. A recess. ,15

I provided on the left side. of hammer 34 allows lug .33. of latchIS tonclear hammer 3,4 as such hammer is rotated rearwardly in aclockwisedia rection. As bolt3 approaches the rear end of its.

.ating bar I4 is then carried forwardly and cam slot I8.'raises h-ammer latch I9 ina counterclockwise direction so that lug- 33 will be raisedoutof engagement with hammer 34; Hencethe bias of hammer spring 4|) drives hammer 34 forwardly to strike a firing pin (not shown) Y The cooking of the hammer is accomplished near the endof the recoil stroke as explained above and while the hammer 34 is rotatin ins clockwise direction the latch l9 is rotating cQunteIQlQcKWi eLWher by thelue 3 of latch.

passes arcuately through recess of hammer 34 and stops a short distance in front of the hammer below recess i5. Therefore when the bolt 2 starts forwardly into the battery position, the hammer also starts forwardly but after the hammer travels a short distance it is stopped and held by the lug 33 of latch I9 until the actuating bar It rotates latch l9 clockwise thereby disengaging such hammer.

It is desired to point out that in semi-automatic fire, lug 33 of latch I9 is similarly disengaged from hammer 35 but due to the high speed of the action, such takes place before trigger 2| can be released and pulled again, hence latch I5 is in efi'ect inoperative in semi-automatic fire as far as the operator is concerned.

From the foregoing description it is readily apparent to one skilled in the art that a simple, efiective fire control mechanism to permit full automatic fire or semi-automatic fire is hereby provided. Further, such mechanism can be readily adapted to firearms arranged to fire only semi-automatically or such mechanism can be readily adapted to any new design of firearm requiring selective full or semi-automatic fire con trol.

I claim:

1. In a firing mechanism for an automatic firearm, a selector member rotatably mounted on the firearm, means for securing said selector memher in a selected one of two angularly displaced positions, an eccentric portion on said selector member, and a scar pivotally mounted on said eccentric portion whereby operation of said selector selectively positions said sear in either a semi-automatic or an automatic fire position.

2. In an automatic firearm, in combination, a spring biased hammer pivotally mounted on the firearm for movement between a cocked and firing position, a firing condition selector member rotatably mounted on the firearm for rotation between two angularly displaced positions, a scar pivotally mounted on said selector and engageable with said hammer to retain said hammer in a cooked position, trigger means for releasing said sear from said hammer, and an eccentric portion on said selector member cooperatin with said sear to selectively position said sear in either an automatic or semi-automatic firing relationship to said hammer by rotation of said selector between its said two positions.

3. In an automatic firearm, in combination, a

spring biased hammer movably mounted in the firearm, a trigger pivotally mounted on a transverse pin in the firearm, a sear having a slot-like hole therein, and said transverse pin having an eccentric portion formed thereon for cooperatin with said slot-like hole whereby said sear can be movably mounted on said trigger for movement between a semi-automatic position wherein said sear may re-engage said hammer in the pulled position of said trigger and an automatic position wherein said sear is not re-engageable with said hammer in the pulled position of said trigger.

4. In an automatic firearm, in combination, a spring biased hammer pivotally mounted on the firearm for movement between a cooked and a firing position, a trigger pivotally mounted on the firearm, a sear having a slot-like hole therein, a selector member rotatably mounted in said trigger in transverse relationship and cooperating with said slot-like hole in said sear to movably mount said scar on said trigger, one end of said sear being engageable with said hammer in the unpulled position of said trigger, said trigger bein constructed and arranged to release said end of the sear from said hammer by pulling movement of said trigger, means for resiliently positioning said selector in either of two angularly displaced positions, and an eccentric portion on said selector member cooperating with said sear to selectively position said sear in a semiautomatic fire position relative to said hammer wherein said sear may re-engage said hammer while said trigger is pulled or in an automatic fire position wherein said sear is maintained out of engagement with said hammer while said trigger is pulled.

ALONZO F. GAIDOS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,324,125 Van Horn et a1 July 13, 1943 2,371,012 Woodhull Mar. 6, 1945 FOREIGN PATENTS Number Country Date 231,050 Great Britain Mar. 26, 1925 

